This invention relates to tread pattern for a vehicle tire with at least one circumferential longitudinal groove and transverse grooves that define tread blocks therebetween.
The tread pattern for a vehicle tire typically includes at least one circumferential longitudinal groove and transverse grooves that run perpendicularly or diagonally relative to the circumferential longitudinal groove. The longitudinal and transverse grooves define the boundaries of the tread blocks therebetween. The surface of the tread block which comes into contact with the ground transmits traction and braking forces. The edges of the tread block which contact the road surface, as well as any additional edges added by way of slots or sipes in the contact surface of the tread block, enhance traction under wet conditions. The sides of the tread blocks facing the circumferential grooves are typically flat and smooth. In other instances, however, such as tires designed specifically for snow conditions, the density of the vertical edges in the circumferential direction is increased by slots or sipes in these side walls.
During the tire-making process, the grooves of the tread pattern are formed by metallic elements of the molds and the spaces between these metallic elements form the tread blocks. To change the profile of the tread blocks, the metallic elements must be replaced. This replacement usually translates into downtime and expense for the tire-making facility.
Accordingly, to convert a tire manufacturing line that is producing tires with substantially flat tread blocks into one that can produce snow tires with slots or sipes in the tread blocks, the metallic elements must be replaced or substantially modified. Specifically, the metallic elements must be provided with projections corresponding to the desired slots or sipes. Also, depending on the size, shape and arrangement of these sipes or slots, the stiffness of the tread block may be reduced. Furthermore, the footprint area, percent void and/or appearance of the tread block may be compromised when compared to an analogous tread block without such sipes or slots.
The inventor therefore appreciated that a need remains for a tire having a tread pattern with an increased edge density that could be made without the conversion of the mold being overly time consuming or expensive.
A need exists for a tire having a tread pattern with an increased edge density that could be made without the conversion of the mold being overly time consuming or expensive.
The present invention provides a tread pattern including tread blocks having projections projecting from the sidewalls into the circumferential groove. The width of each of the projections is preferably less than 10% of the circumferential dimension of the respective tread block. To convert a mold having elements that produce tread blocks with substantially flat sidewalls into a mold that produce this tread pattern, channels are machined into the sidewalls of the mold elements. In this manner, an existing mold can be retrofitted in a matter of hours and with relatively inexpensive equipment. Thus, the present invention provides a tread pattern having an increased edge density that can be made without the conversion of the mold being overly time consuming or expensive. Moreover, the present invention allows an increased edge density without reducing the stiffness of the tread block and/or compromising its footprint area, percent void and/or appearance when compared to an analogous tread block.